Storage system and storage control apparatus

ABSTRACT

In this invention, when execution of an special function executable only by a second storage control apparatus connected to a first storage control apparatus is requested by a higher-level apparatus, the special function is caused to be executed by a second storage control apparatus, and appropriate load balancing is achieved. An executing apparatus judgment section, upon receiving an execution request from a host, uses a function management section and a state detection section to decide which storage control apparatus should execute the function. An execution instruction section issues an instruction to execute the function to the function execution section of the storage control apparatus determined to be the executing apparatus. By this means, even in the case of an special function executable only by a storage control apparatus, the function can be caused to be executed. Hence a connection source storage control apparatus can appear to have increased functionality, without installing the function on the connection source storage control apparatus.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application relates to and claims priority from Japanese PatentApplication No. 2006-15894, filed on Jan. 25, 2006, the entiredisclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a storage system and to a storagecontrol apparatus.

2. Description of the Related Art

Because the quantity of data to be managed by for example corporations,government organizations, educational institutions and other userscontinues to increase on a daily basis, the storage volume required bysuch users also increases continuously. As a result, users add newstorage devices to storage control apparatuses, or introduce new storagecontrol apparatuses having storage resources with still greatercapacities.

By thus utilizing a plurality of storage control apparatuses, usersintermix a plurality of storage control apparatuses within a storagesystem. Hence technology is provided to a higher-level apparatus bymeans of which, by connecting a first storage control apparatus toanother storage control apparatus, storage resources within the storagesystem are virtualized, so that a plurality of storage controlapparatuses can be utilized effectively (Japanese Patent Laid-open No.10-283272, Japanese Patent Laid-open No. 2004-220450, Japanese PatentLaid-open No. 2005-92424).

SUMMARY OF THE INVENTION

In the prior art described in the above references, functions forvirtualizing storage resources within a storage system by means of afirst storage control apparatus are disclosed. In Japanese PatentLaid-open No. 2005-92424, technology is disclosed in which a secondstorage control apparatus is caused to execute backup processing andother heavy-load processing, so as to lighten the load on a firststorage control apparatus.

However, in the case of the prior art described in the above references,there remains room for study regarding which of the storage controlapparatuses within the storage system should optimally be caused toexecute functions requested by the higher-level apparatus.

For example, a group of functions of a storage system can be broadlydivided into common functions which can be executed by each of thestorage control apparatuses, and special functions which can be executedonly by prescribed storage control apparatuses. When a function theexecution of which is requested by a higher-level apparatus is a commonfunction, the function can be executed by any of the storage controlapparatuses.

However, when execution of the common functions is concentrated on acertain single storage control apparatus, and a plurality of commonfunctions are each started within the one storage control apparatus,processing performance declines. Hence the performance of the storagesystem as a whole with respect to the common functions declines.

Further, in the case of the prior art described in the references, eachof the functions of the first storage control apparatus can be utilized,but an special function which can be executed only by a second storagecontrol apparatus cannot be effectively utilized. This is because when ahigher-level apparatus requests a function which cannot be executed bythe first storage control apparatus, the first storage control apparatusmay immediately return an error response.

This invention was devised in light of the above problems, and has as anobject the provision of a storage system and storage control apparatusenabling appropriate distribution of a processing load among a pluralityof storage control apparatuses. A further object of the invention is toprovide a storage system and storage control apparatus in which, when ahigher-level apparatus requests execution of an special function whichcan be executed only by a second storage control apparatus connected toa first storage control apparatus, the second storage control apparatuscan be made to execute the special function. Further objects of theinvention will become apparent from the explanations of the aspectswhich follow.

SUMMARY OF THE INVENTION

In order to resolve the above problems, a storage system according tothis invention is provided with a first storage control apparatus whichaccepts requests from a higher-level apparatus, and at least one secondstorage control apparatus, connected to the first storage controlapparatus; the first storage control apparatus can supply a higher-levelapparatus a second storage area of a second storage control apparatus asa first storage area of the first storage control apparatus. Further,the storage area is provided with a state detection section, whichdetects the respective state of the first storage control apparatus andof the second storage control apparatuses; a function management sectionfor managing functions which can be executed by the first storagecontrol apparatus and by the second storage control apparatus; anexecuting apparatus judgment section, which, when execution of aprescribed function is requested by a higher-level apparatus, uses thestate detection section and function management section to judge whichstorage control apparatus among the storage control apparatuses shouldexecute the prescribed function, based on the state of the storagecontrol apparatuses and the details of the prescribed function; and, anexecution instruction section, which instructs the storage controlapparatus determined by the executing apparatus judgment section to bethe storage control apparatus to execute the prescribed function.

In an aspect of the invention, a function selection section is furtherprovided to select in advance the functions which can be executed amongthe functions with which each of the storage control apparatuses isprovided, and the function management section manages, for each of thestorage control apparatuses, the functions selected by the functionselection section.

In an aspect of the invention, an execution mode setting section isfurther provided, to set the execution mode of functions which can beexecuted by each of the storage control apparatuses.

In an aspect of the invention, conditions for causing the execution of afunction are set in advance for each of the executable functions of eachof the storage control apparatuses, and the executing apparatus judgmentsection judges which storage control apparatus among the storage controlapparatuses should execute a prescribed function based on the state ofeach storage control apparatus and the conditions associated in advancewith the prescribed function.

In an aspect of the invention, a condition is set such that, when theload of the first storage control apparatus is equal to or greater thana first threshold set in advance, the prescribed function is set to beexecuted by a second storage control apparatus.

In an aspect of the invention, a condition is set such that, when theload of a second storage control apparatus is less than a secondthreshold set in advance, the prescribed function is set to be executedby the second storage control apparatus.

In an aspect of the invention, a condition is set such that, when theload of the first storage control apparatus is equal to or greater thana first threshold set in advance, and moreover the load of a secondstorage control apparatus is less than a second threshold set inadvance, the prescribed function is set to be executed by the secondstorage control apparatus.

In an aspect of the invention, functions which can be executed by thefirst storage control apparatus and by the second storage controlapparatuses can be divided into common functions which can be executedby each of storage control apparatuses and special functions which canbe executed by only one among the storage control apparatuses, and foreach common function, a setting can be set indicating which storagecontrol apparatus among the storage control apparatuses is to executethe function.

In an aspect of the invention, functions which can be executed by thefirst storage control apparatus and by the second storage controlapparatuses can be divided into common functions which can be executedby each of storage control apparatuses and special functions which canbe executed by only one among the storage control apparatuses, and theexecuting apparatus judgment section (1) causes execution of commonfunctions, which the first storage control apparatus can execute commonfunctions, and causes second storage control apparatuses to executecommon functions based on the state of the second storage controlapparatuses, when the first storage control apparatus cannot executecommon functions, and (2) causes execution of special functions bysecond storage control apparatuses, based on the state of the secondstorage control apparatuses.

In an aspect of the invention, a prescribed function is a function whichis accompanied by data conversion; the first storage control apparatusand second storage control apparatus are capable of executing prescribedfunctions, and when the first storage control apparatus executes aprescribed function, execution of the prescribed function by the firststorage control apparatus is set to valid and execution of theprescribed function by the second storage control apparatus is set toinvalid, and when the second storage control apparatus executes aprescribed function, execution of the prescribed function by the firststorage control apparatus is set to invalid and execution of theprescribed function by the second storage control apparatus is set tovalid.

In an aspect of the invention, a function which is accompanied by dataconversion can comprise at least one of compression and encryption.

In an aspect of the invention, a higher-level apparatus requestsexecution of a prescribed function to a first storage area, and when asecond storage control apparatus is determined to be the executingapparatus by the executing storage control apparatus judgment section,the execution instruction section issues an execution instruction tocause execution of the prescribed function to a second storage area.

In an aspect of the invention, a plurality of second storage controlapparatuses are each connected to the first storage control apparatus soas to enable communication, and moreover each of the second storagecontrol apparatuses are interconnected so as to enable communication;the execution instruction section issues an execution instruction to asecond storage control apparatus determined to be the executing storagecontrol apparatus by the executing apparatus judgment section from amongthe plurality of second storage control apparatuses, to cause executionof a prescribed function; and the execution instruction thus issued istransmitted via second storage control apparatus not selected as theexecuting storage control apparatus by the executing apparatus judgmentsection, to the second storage control apparatus determined to be theexecuting storage control apparatus.

Here, in this aspect of the invention, the prescribed function conveyedvia the second storage control apparatuses can comprise at least oneamong data copying within a second storage area, and a storage devicepower management function of a second storage area.

A storage control apparatus according to another perspective of theinvention is a storage control apparatus which is connected so as toenable communication with a higher-level apparatus which requestsexecution of prescribed functions and a second storage controlapparatus, a second storage area of the second storage control apparatusbeing able to be provided in virtual form to the higher-level apparatusas a first storage area of the storage control apparatus itself, and thestorage control apparatus comprises a state detection section, whichdetects the state of the storage control apparatus itself and of thesecond storage control apparatus; a function management section formanaging functions which can be executed by the storage controlapparatus itself and by the second storage control apparatus; anexecuting apparatus judgment section, which, when execution of aprescribed function is requested by a higher-level apparatus, uses thestate detection section and function management section to judge whetherthe storage control apparatus itself or the second storage controlapparatus should execute the prescribed function, based on the state ofthe storage control apparatus itself and the second storage controlapparatus and on the details of the prescribed function; and, anexecution instruction section, which instructs the storage controlapparatus determined by the executing apparatus judgment section to bethe storage control apparatus to execute the prescribed function.

A storage system according to still a different perspective of theinvention comprises a first storage control apparatus which acceptsrequests from a higher-level apparatus and a plurality of second storagecontrol apparatuses, connected with the first storage control apparatusso as to enable communication; the first storage control apparatuscomprises at least a first controller, and each of the second storagecontrol apparatuses comprises a second controller to execute specifiedfunctions and a plurality of storage devices.

The first controller provides logical volumes, created on anintermediate storage device, to a higher-level apparatus by associatingone or a plurality of intermediate storage devices, provided in virtualform within the first storage control apparatus, with physical storageareas provided by storage devices of the second storage controlapparatuses. The first controller comprises a volume management table,which manages the relations between logical volumes, and intermediatestorage devices and the storage devices of each of the second storagecontrol apparatuses; a function management table, in which areregistered functions which can be executed by the first storage controlapparatus and by each of the second storage control apparatuses; afunction executing apparatus management table, which sets in advance,for the group of functions which can be executed by any of the secondstorage control apparatuses among the functions registered in thefunction management table, which of the second storage controlapparatuses is to be caused to execute each function; a state detectionsection, which detects the load state of the first storage controlapparatus and of the second storage control apparatuses; an executingapparatus judgment section, which, when execution of a prescribedfunction has been requested by a higher-level apparatus, uses the statedetection section, the function management table, and the functionexecuting apparatus management table to judge which storage controlapparatus among the first storage control apparatus and the secondstorage control apparatuses should execute the prescribed function,based on the state of the first storage control apparatus and secondstorage control apparatuses and on the details of the prescribedfunction; and, an execution instruction section, which instructs thefirst controller or second controller of the storage control apparatusdetermined to be the executing storage control apparatus by theexecuting apparatus judgment section to execute the prescribed function.

At least a portion of the means and portions of this invention can insome cases be executed by a computer program. This computer program canbe distributed in fixed form on various recording media, or can betransmitted over communication media.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram showing the overall concept of thestorage system of an aspect of the invention;

FIG. 2 is an explanatory diagram showing the overall configuration of astorage system;

FIG. 3 is an explanatory diagram showing the hardware configuration of astorage system;

FIG. 4 is an explanatory diagram showing the storage configuration of astorage system;

FIG. 5 is an explanatory diagram showing a volume management table;

FIG. 6 is an explanatory diagram showing a function management table;

FIG. 7 is an explanatory diagram showing a function executing apparatusmanagement table;

FIG. 8 is a user interface explanatory diagram showing a window forfunction selection and a window to set the executing storage controlapparatus;

FIG. 9 is a flowchart showing executing apparatus allocation processing;

FIG. 10 is a flowchart showing the allotment processing in FIG. 9;

FIG. 11 is an explanatory diagram showing the overall configuration of astorage system of a second embodiment;

FIG. 12 is an explanatory diagram showing the contents of tables usedwhen employing a compression function and where each table is held;

FIG. 13 is a flowchart showing processing to compress and store writedata;

FIG. 14 is a flowchart showing processing to read and expand compresseddata;

FIG. 15 is an explanatory diagram showing the overall configuration ofthe storage system of a third embodiment;

FIG. 16 is a flowchart showing compression copy processing;

FIG. 17 is a flowchart showing expansion copy processing;

FIG. 18 is an explanatory diagram showing the overall configuration ofthe storage system of a fourth embodiment; and,

FIG. 19 is a flowchart showing the operation of the storage system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Below, aspects of the invention are explained using the drawings. FIG. 1is an explanatory diagram showing the overall configuration of thestorage system of an aspect. This storage system can be configured usingfor example one connection source storage control apparatus 1 and one ormore connection destination storage control apparatuses 2, 3.

Here, the connection source storage control apparatus 1 corresponds tothe “first storage control apparatus”. The first connection destinationstorage control apparatus 2 and the second connection destinationstorage control apparatus 3 correspond to the “second storage controlapparatuses”. The host computer (hereafter “host”) 4 corresponds to the“higher-level apparatus”. The virtual volume 1B of the connection sourcestorage control apparatus 1 corresponds to the “first storage area”.And, the real volumes 2B, 3B of the connection destination storagecontrol apparatuses 2, 3 correspond to “second storage areas”.

The connection source storage control apparatus 1 accepts and processesvarious requests from the host 4, and returns the results thereof. Aplurality of the connection-destination storage control apparatuses 2, 3are connected to the connection-source storage control apparatus 1. Theconnection source storage control apparatus 1 provides the host 4 withthe real volumes 2B and 3B of the connection destination storage controlapparatuses 2, 3 as if these volumes were the apparatus' own volume 1B.The connection source storage control apparatus 1 executes dataprocessing (functions) requested by the host 4, and returns the resultsthereof to the host 4. In this way, the connection source storagecontrol apparatus 1 serves as an interface representing the storagesystem, in a storage system in which a plurality of storage controlapparatuses 1, 2, 3 are intermixed.

The configuration of the connection source storage control apparatus 1is explained. The connection source storage control apparatus 1 cancomprise, for example, a control section 1A, a virtual volume 1B, ahigher-level communication section 1C, and a lower-level communicationsection 1D. The higher-level communication section 1C and lower-levelcommunication section 1D are placed outside the control section 1A, butthe communication sections 1C, 1D may be provided within the controlsection 1A.

As stated below, the connection source storage control apparatus 1 neednot comprise a physical storage area for storage of user data. Hence theconnection source storage control apparatus 1 can be configured as adisk array subsystem, or can be configured as a network switch.

The higher-level communication section 1C is connected to the host 4 viathe communication network CN1, and performs bidirectional datacommunication with the host 4. As the communication network CN1, forexample, a LAN (Local Area Network) or SAN (Storage Area Network) orsimilar can be used. That is, the higher-level communication section 1Cand host 4 can perform data communication using TCP/IP (TransmissionControl Protocol/Internet Protocol) and FCP (Fibre Channel Protocol).

The lower-level communication section 1D is connected to the firstconnection destination storage control apparatus 2 via the communicationnetwork CN2. The lower-level communication section 1D is also connectedto the second connection destination storage control apparatus 3 via thecommunication network CN3. As the communication networks CN2 and CN3,for example, a LAN, SAN or similar can be used. The communicationnetworks CN1, CN2, CN3 can be configured as the same network.

The virtual volume 1B is a logical storage device used by the host 4,and is also called a logical volume. In the following explanation, thevirtual volume 1B may be called a logical volume 1B. Data (user data)utilized by the host 4 is stored in the virtual volume 1B. However, thevirtual volume 1B is not provided with a physical entity. The user datais actually stored by the real volume 2B of the first connectiondestination storage control apparatus 2.

By mapping the real volume 2B to a virtual volume 1B, the address spaceof the virtual volume 1B is associated with the address space of thereal volume 2B. When the host 4 specifies a prescribed address of thevirtual volume 1B and transmits write data, the write data istransferred to the first connection destination storage controlapparatus 2, and is written to the address in the real volume 2Bassociated with the prescribed address. When the host 4 specifies theprescribed address in the virtual volume 1B and requests data reading,data is read from the address in the real volume 2B associated with theprescribed address and is transmitted from the first connectiondestination storage control apparatus 2 to the connection source storagecontrol apparatus 1. The connection source storage control apparatus 1transmits the data received from the first connection destinationstorage control apparatus 2 to the host 4.

In this way, the host 4 can read data from and write data to the virtualvolume 1B without at all being aware of the location in the storagesystem of the physical entity of the virtual volume 1B. The function inwhich, by associating the real volume 2B of the connection destinationstorage control apparatus 2 with the virtual volume 1B of the connectionsource storage control apparatus 1, the real volume 2B, existing outsidethe connection source storage control apparatus 1 can be provided to thehost 4 as a logical volume within the connection source storage controlapparatus 1, is in this specification called an external connectionfunction.

The configuration of the control section 1A is explained. In addition tothe above-described external connection function, the control section 1Acan for example be provided with a function execution section 1A1,executing apparatus judgment section 1A2, function management section1A3, state detection section 1A4, execution instruction section 1A5,execution mode setting section 1A6, and function selection section 1A7.

The function execution section 1A1 executes functions requested by thehost 4. Here, a function may for example be a local volume copyfunction, remote copy function, snapshot function, encryption (includingdecryption) function, compression (including expansion) function, orsimilar.

A local volume copy function is a function to copy either all of or aportion of the data from a copy source volume to a copy destinationvolume, when both the copy source volume and the copy destination volumeexist within the same subsystem. Hence the local volume copy function issometimes also called an intra-subsystem volume copy function.

A remote copy function is a function to copy either all of or a portionof the data from a copy source volume to a copy destination volume, whenthe copy source volume and the copy destination volume exist indifferent subsystems. The remote copy function can also be called aninter-subsystem volume copy function. The remote copy function can alsobe broadly divided into a synchronous remote copy function and anasynchronous remote copy function. The synchronous remote copy functionis a function in which, after confirming completion of write processingat the data transfer destination (the storage control apparatus havingthe copy destination volume) in response to a write request from thehigher-level apparatus to the copy source volume, a write completionresponse is issued to the higher-level apparatus. The asynchronousremote copy function is a function in which, in response to a writerequest to the copy source volume from the higher-level apparatus, awrite completion response is issued to the higher-level apparatus,without confirming the completion of write processing at the datatransfer destination.

A snapshot function is a function in which a static storage image of alogical volume 1B at a specified prescribed point in time is created.The snapshot function may be realized by a method of using the volumecopy function to create and save a synchronous volume, or by a method ofsaving (copying) old data in an area for writing to another area when awrite request from the higher-level apparatus has occurred and thenwriting the new data, or by a method of writing new data to another areawhen there is a write request to a static area from the higher-levelapparatus.

A migration function is a function in which all or a portion of aspecified prescribed logical volume 1B is moved to another logicalvolume 1B, without changing the host access path. Methods of realizingthe migration function include a method of using a volume copy functionor similar to create a synchronized volume and then changing data accessby the host from the movement source to the movement destination, and amethod of first changing the access to the movement destination, andthen copying data from the movement source to the movement destinationin order.

An encryption function is a function for encrypting data based on aprescribed encryption algorithm, and for decrypting encrypted data. Acompression function is a function for performing data compression basedon a compression algorithm, and for expanding compressed data.

The function execution section 1A1 executes all of or a portion of theabove-described functions. Of the above functions, those functionsprovided in common to the connection source storage control apparatus 1and to each of the connection destination storage control apparatuses 2,3 are called common functions F1, and functions other than commonfunctions F1 can be called special functions F2. In the example shown inFIG. 1, the connection source storage control apparatus 1 can executeonly common functions F1, and each of the connection destination storagecontrol apparatuses 2, 3 can execute common functions F1 and specialfunctions F2. Hence special functions F2 can also be called functionswhich can be executed only by connection destination storage controlapparatuses 2, 3.

The executing apparatus judgment section 1A2 judges which of the storagecontrol apparatuses 1, 2, 3 should execute a function the execution ofwhich has been requested by the host 4. The executing apparatus judgmentsection 1A2 uses the function management section 1A3 and state detectionsection 1A4 to select one storage control apparatus which is to executethe function requested by the host 4.

The function management section 1A3 manages functions which can beexecuted (used by) each of the storage control apparatuses 1, 2, 3. Thefunction selection section 1A7 selects which of the functions can beexecuted among the plurality of functions of each of the storage controlapparatuses 1, 2, 3. In other words, the function management section 1A3manages functions selected for each of the storage control apparatuses1, 2, 3 by the function selection section 1A7. Hence the executingapparatus judgment section 1A2 uses the function management section 1A3to ascertain which storage control apparatus can execute whichfunctions.

The state detection section 1A4 detects the state of each of the storagecontrol apparatuses 1, 2, 3. State may be, for example, the load stateof the storage control apparatuses 1, 2, 3. Parameters used to detectload state may be, for example, the number of data input/output requestsper unit time (IOPS), the CPU (Central Processing Unit) usage rate, thecache memory usage rate, and similar. A plurality of such parameters canbe combined to judge the load state. The state of a storage controlapparatus is not limited to the load state; for example, whether thestorage control apparatuses 1, 2, 3 is in operation, or similarinformation can be used. This is because when an apparatus is halted formaintenance operations or similar, a function requested by the host 4cannot be executed even when the storage control apparatus is selected.

The executing apparatus judgment section 1A2 can use the state detectionsection 1A4 to ascertain the state of each of the storage controlapparatuses 1, 2, 3. The executing apparatus judgment section 1A2selects the apparatus for execution of a function the execution of whichhas been requested, based on which of the storage control apparatuses 1,2, 3 is capable of executing the function execution of which has beenrequested by the host 4, and based on the current state of the storagecontrol apparatuses 1, 2, 3.

The execution instruction section 1A5 issues an instruction to a storagecontrol apparatus selected by the executing apparatus judgment section1A2, to cause execution of a function execution of which has beenrequested by the host 4. If the connection source storage controlapparatus 1 is selected as the executing apparatus, the executioninstruction section 1A5 provides the execution instruction to thefunction execution section 1A1. If either of the connection destinationstorage control apparatuses 2, 3 is selected as the executing apparatus,the execution instruction section 1A5 provides the execution instructionto the selected connection destination storage control apparatus 2 or 3.

The execution mode setting section 1A6 sets the execution mode for anexecutable function. When a certain function has a plurality ofexecution modes, and switching between the execution modes is possible,the execution mode setting section 1A6 sets which one among theexecution modes is to be selected. For example, in the case of acompression function which can be switched between a compression mode tocompress data and an expansion mode to expand data during execution, theexecution mode setting section 1A6 selects one of these execution modes.Similarly in the case of an encryption function which can be switchedbetween an encryption mode to encrypt data and a decryption mode todecrypt encrypted data during execution, the execution mode settingsection 1A6 selects one of these modes.

Next, the configuration of the first connection destination storagecontrol apparatus 2 is explained. The first connection destinationstorage control apparatus 2 provides a physical storage area to theconnection source storage control apparatus 1. Hence the firstconnection destination storage control apparatus 2 comprises a controlsection 2A, real volume 2B, and higher-level communication section 2C.Further, the first connection destination storage control apparatus 2can operate linked with the second connection destination storagecontrol apparatus 3. For this purpose, the first connection destinationstorage control apparatus 2 comprises a lower-level communicationsection 2D. The first connection destination storage control apparatus 2is for example configured as a disk array subsystem.

The control section 2A controls operation of the first connectiondestination storage control apparatus 2, and comprises a functionexecution section 2A1. The function execution section 2A1 can executecommon functions F1 and special functions F2, and executes specifiedfunctions.

The real volume 2B is a logical storage device (logical volume) linkedto a physical entity for storage of data. In this specification, alogical volume linked to a physical entity may be called a real volume,and a logical volume indirectly linked to a physical entity may becalled a virtual volume. More specifically, the physical storage areasof each of a plurality of storage devices such as hard disk drives arecombined and virtualized, and a real volume is created on the storagearea of this virtualized physical storage device (also called anintermediate storage device).

The higher-level communication section 2C is connected to the connectionsource storage control apparatus 1 via the communication network CN2,and performs bidirectional data communication with the connection sourcestorage control apparatus 1. The lower-level communication section 2D isconnected to the second connection destination storage control apparatus3 via the communication network CN4, and performs bidirectional datacommunication with the second connection destination storage controlapparatus 3. As the communication network CN4, a SAN, LAN, or similarcan be used. The communication network CN4 and the communicationnetworks CN1, CN2, CN3 can be configured as the same network.

The second connection destination storage control apparatus 3, similarlyto the first connection destination storage control apparatus 2,provides a physical storage area to the connection source storagecontrol apparatus 1. Hence the second connection destination storagecontrol apparatus 3, similarly to the first connection destinationstorage control apparatus 2, can for example be configured as a diskarray subsystem having a control section 3A and real volume 3B. Due tolimitations of space, the configuration of the communication portion isomitted, but the second connection destination storage control apparatus3 also has a higher-level communication portion. When connecting stillanother storage control apparatus downstream from the second connectiondestination storage control apparatus 3, the second connectiondestination storage control apparatus 3 is provided with a lower-levelcommunication portion.

The control section 3A controls operation of the second connectiondestination storage control apparatus 3, and comprises a functionexecution section 3A1. The function execution section 3A1 can executecommon functions F1 and special functions F2, and executes specifiedfunctions. The real volume 3B can be associated with a virtual volume 1Bof the connection source storage control apparatus 1. An externalconnection function can also be provided in the first connectiondestination storage control apparatus 2, and a real volume 3B of thesecond connection destination storage control apparatus 3 associatedwith a virtual volume within the first connection destination storagecontrol apparatus 2, as in an embodiment explained below.

Next, operation of the storage system is explained. Data read processingand write processing by an external connection function has already beendiscussed and so is omitted. The host 4 issues a request to theconnection source storage control apparatus 1 for execution of aprescribed function other than a read request or a write request (avolume copy function, compression function, or similar). This executionrequest comprises information to identify the volume to which theprescribed function is to be applied.

The executing apparatus judgment section 1A2, upon receiving theexecution request from the host 4, uses the function management section1A3 and state detection section 1A4 to decide which of the storagecontrol apparatuses 1, 2, 3 should be made to execute the functionexecution of which has been requested.

Execution conditions can be set in advance for all or a portion of theplurality of functions managed by the function management section 1A3.Conditions can be, for example, “cause a connection destination storagecontrol apparatus to perform execution when the load on the connectionsource storage control apparatus is high”; “when the load on aconnection destination storage control apparatus is low, have thatconnection destination storage control apparatus perform proxyprocessing”; and “when the load on the connection source storage controlapparatus is high, and moreover the load on a connection destinationstorage control apparatus is low, have that connection destinationstorage control apparatus execute the function”.

The executing apparatus judgment section 1A2 confirms that theprescribed function execution of which has been requested can beexecuted by any of the storage control apparatuses 1, 2 or 3, and judgeswhether the current state of storage control apparatuses capable ofexecution satisfy the execution conditions. The executing apparatusjudgment section 1A2 then selects a storage control apparatus satisfyingthe execution conditions as the executing apparatus.

The execution instruction section 1A5 issues an instruction to executethe prescribed function to the function execution section 1A1, 2A1, or3A1 of the storage control apparatus selected as the executingapparatus. The execution instruction section 1A5 issues the executioninstruction either with the execution request from the host 4unmodified, or with the execution request form the host 4 converted intoanother execution request.

For example, suppose that the connection source storage controlapparatus 1 has two virtual volumes 1B, and that one virtual volume 1Bis associated with the real volume 2B of the first connectiondestination storage control apparatus 2, while the other virtual volume1B is associated with the real volume 3B of the second connectiondestination storage control apparatus 3. With this configuration,suppose that the host 4 requests execution of data copying from onevirtual volume 1B to the other virtual volume 1B.

When the connection source storage control apparatus 1 is selected asthe executing apparatus, the execution instruction section 1A5 issues aninstruction to the function execution section 1A1 to execute the localvolume copy function. The function execution section 1A1 writes dataread from one of the virtual volumes 1B to the other virtual volume 1Bby executing the local volume copy function.

When the first connection destination storage control apparatus 2 isselected as the executing apparatus, the execution instruction section1A5 issues an instruction to the function execution section 2A1 toexecute the remote copy function. The function execution section 2A1transmits data read from the real volume 2B to the second connectiondestination storage control apparatus 3 and causes the data to be storedin the real volume 3B by means of the remove copy function.

In this way, the execution instruction section 1A5 can convert executionrequests from the host 4, based on the details of the storage controlapparatus selected as the executing apparatus and details of theprescribed function (the details of processing expected by the host 4),so as to obtain the execution result desired by the host 4.

By means of the above-described configuration, this aspect has thefollowing advantageous results. First, in this aspect the storagecontrol apparatus which is to execute the prescribed function isselected based on the details of the prescribed function execution ofwhich has been requested by the host 4, and based on the state of thestorage control apparatuses 1, 2, 3. Hence increases in the processingload of a specific storage control apparatus can be suppressed, andloads can be distributed more appropriately within the storage system.

Second, when in this aspect the host 4 requests execution of an specialfunction F2 which can be executed only by the connection destinationstorage control apparatuses 2 and 3, the appropriate executing apparatusis selected and caused to execute the function according to the state ofthe connection destination storage control apparatuses 2, 3. Hence evenin the case of a function with which the connection source storagecontrol apparatus 1 is not provided, if the function F2 can be executedby the connection destination storage control apparatuses 2, 3, thefunction F2 can be caused to be executed. By this means, functions F2which can be executed only by the connection destination storage controlapparatuses 2, 3 can be effectively utilized, and the connection sourcestorage control apparatus 1 can appear to be executing the function,even when the function F2 is not actually installed in the connectionsource storage control apparatus 1.

In order to use a function F2 which is not installed in the connectionsource storage control apparatus 1, but is installed only in theconnection destination storage control apparatuses 2, 3, an interface toreceive instructions for execution of the function F2 is necessary. Thisinterface to receive instructions to execute a function which is notinstalled can for example be provided in the higher-level communicationsection 1C. As the method of installation of such an interface, forexample, a method of installation of a common interface recommended by astandardization body or similar, or a method of associating in peculiarread commands and write commands for a specific address in a speciallogical device with instructions for execution of the function F2 in theconnection destination storage control apparatuses 2, 3, or a method ofdefining the function in advance as a vendor-specific command, or amethod of re-installing in the connection source storage controlapparatus 1 an interface used by the connection destination storagecontrol apparatuses 2 and 3, can be employed.

Focusing on the above-described second advantageous result, this aspectcan for example be expressed as “a storage system, comprising a firststorage control apparatus (1) which accepts requests from a higher-levelapparatus (4) and one or more second storage control apparatuses (2,3)connected to the first storage control apparatus to enablecommunication, and wherein the first storage control apparatus canprovide to the higher-level apparatus a second storage area (2B) of thesecond storage control apparatuses as a first storage area (1B) of thefirst storage control apparatus; and further comprising:

a reception section (1C) which, when a request for execution of afunction (F2) which is installed only on a second storage controlapparatus is issued from the higher-level apparatus, receives theexecution instruction;

a function management section (1A3) to manage functions which can beexecuted by the first storage control apparatus and by the secondstorage control apparatuses;

an executing apparatus judgment section (1A2), which, when execution ofa prescribed function (F2) has been requested by the higher-levelapparatus via the reception section, selects a second storage controlapparatus capable of executing the prescribed function by using thefunction management section; and,

an execution instruction section, which issues an instruction forexecution of a prescribed function to the connection destination storagecontrol apparatus selected as the executing apparatus by the executingapparatus judgment section”.

Instructions from the host 4 to the storage control apparatus 1 andinstructions from the storage control apparatus 1 to the storage controlapparatuses 2, 3 can employ the so-called in-band method or out-of-bandmethod. That is, instructions can be provided via a data input/outputnetwork (in-band method), or instructions can be provided via amanagement network (out-of-band method). Hereafter, this aspect isexplained in greater detail.

Embodiment 1

FIG. 2 is an explanatory diagram showing the overall configuration ofthe storage system of this embodiment. This storage system can beconfigured to comprise, for example, one connection source storagecontrol apparatus 100, a plurality of connection destination storagecontrol apparatuses 200, one or a plurality of hosts 10, and one or aplurality of management servers 20.

The correspondence between the configuration shown in FIG. 2 and thatshown in FIG. 1 is as follows. The connection source storage controlapparatus 100 corresponds to the connection source storage controlapparatus 1 in FIG. 1; the first connection destination storage controlapparatus 200 corresponds to the first connection destination storagecontrol apparatus 2 shown in FIG. 1; the second connection destinationstorage control apparatus 300 corresponds to the second connectiondestination storage control apparatus 3 shown in FIG. 1; and the host 10corresponds to the host 4 in FIG. 1. The virtual volume 113 correspondsto the virtual volume 1B in FIG. 1, and the real volumes 213, 313correspond to the real volumes 2B, 3B in FIG. 1.

The connection source storage control apparatus 100 is an apparatuswhich represents the connection destination storage control apparatuses200, 300 to accept various commands from the host 10. The connectiondestination storage control apparatuses 200, 300 provide real volumes213, 313 to the connection source storage control apparatus 100. Detailsof the storage control apparatuses 100, 200, 300 are explained below.

The host 10 is a computer apparatus which is for example configured as apersonal computer, workstation, mainframe, or similar. The host 10 canfor example be provided with a program to manage a RAID (Redundant Arrayof Independent Disks), a program to manage paths, and variousapplication programs.

The host 10 accesses the volume 113 of the connection source storagecontrol apparatus 100 and performs data reading and writing. Themanagement server 20 is connected to the host 10 and to the storagecontrol apparatuses 100, 200, 300 via a communication network formanagement CN13.

The management server 20 manages the state of each host 10 and of eachof the storage control apparatuses 100, 200, 300. A LAN can for examplebe used as the communication network for management CN3.

The host 10 and the connection source storage control apparatus 100 areconnected via a SAN, for example, or another communication network CN11.The connection source storage control apparatus 100 is connected to eachof the connection destination storage control apparatuses 200, 300 viafor example a SAN or another communication network CN12.

Here, a SAN may be an FC_SAN using FCP, or may be an IP_SAN using IP(the Internet Protocol). Also, CN11 and CN12 can be configured asseparate SANs, as for example when the network CN11 is an FC_SAN and thenetwork CN12 is an IP_SAN. Also, CN11 and CN12 can be integrated, and acommon network can be used to connect the host 10 to the storage controlapparatuses 100, 200, 300 and to connect the storage control apparatuses100, 200, 300 to each other.

FIG. 3 is an explanatory diagram showing the hardware configuration ofthe storage control apparatuses 100, 200, 300. FIG. 3 primarily shows anexample of the configuration of a connection source storage controlapparatus 100. The connection source storage control apparatus 100 canbe configured as a disk array subsystem comprising a controller 101 andstorage section 110, for example. The connection source storage controlapparatus 100 can also be configured as an intermediate apparatus, suchas a switching device.

The controller 101 controls operation of the connection source storagecontrol apparatus 100. The controller 101 can be configured to comprise,for example, a plurality of channel adapters (hereafter “CHAs”) 120, aplurality of disk adapters (hereafter “DKAs”) 130, cache memory 140,shared memory 150, a connection control section 160, and a serviceprocessor (hereafter “SVP”) 170. The configuration of the controller 101is not limited to that shown in FIG. 3. Any configuration may beemployed so long as communication functions between the host 10 and theconnection destination storage control apparatuses 200, 300, as well asan external connection function, executing apparatus judgment function,and similar are realized.

The CHA 120 controls data communication with the host 10. The CHA 120can be configured as a computer apparatus comprising, for example, amicroprocessor, memory, a protocol chip, a data transfer chip, andsimilar. The CHA 120 comprises a plurality of communication ports 121.Each communication port 121 is allocated a network address, such as forexample an IP address or a WWN (World Wide Name).

The communication ports 121 can be set as, for example, initiator portsor target ports. A communication port 121 set as a target port isconnected to the host 10. A communication port 121 set as an initiatorport (external connection port) is connected to the connectiondestination storage control apparatuses 200, 300. The host 10 and theconnection source storage control apparatus 100, and the connectionsource storage control apparatus 100 and connection destination storagecontrol apparatuses 200, 300, may be connected by a plurality ofcommunication paths. By this means the communication load can bedistributed, and fault tolerance can be improved.

The DKA 130 controls data communication with the storage section 110.Similarly to the CHA 120, the DKA 130 is configured as a computerapparatus comprising a microprocessor, memory and similar. Thecommunication ports 131 of the DKA 130 are connected to the storagesection 110 via the communication network CN21.

Cache memory 140 stores write data received from the host 10 and readdata read from the storage section 110. Shared memory 150 stores variouscontrol information and management information necessary to controloperation of the storage control apparatus 100. A plurality of cachememory units 140 may be provided, to realize redundant storage of datanot written to the storage section 110 (so-called “dirty data”). Also,cache memory 140 and shared memory 150 may be configured as the samememory package. And, a portion of a certain memory unit may be used as acontrol memory area, and the remaining portion used as a cache memoryarea.

The connection control section 160 is configured as for example acrossbar switch or similar. The connection control section 160 connectseach of the CHAs 120 and each of the DKAs 130 to cache memory 140 andshared memory 150.

The SAV 170 is connected to the CHAs 120 and the LAN interface 180 viainternal LAN and others. The SVP 170 collects various status and otherinformation within the storage control apparatus 100, either regularlyor irregularly, and outputs warning signals, analysis results andsimilar based on the collected information.

In FIG. 3, although not shown due to limitations of space, the SVP 170is connected to a management terminal 31 shown in FIG. 2. The managementterminal 31 is for example configured as a personal computer, mobilecomputer, or similar. The management terminal 31 can ascertain the statewithin the storage control apparatus 100 via the SVP 170. The user canalso modify settings of the storage control apparatus 100 from themanagement terminal 31 via the SVP 170.

The LAN interface 180 is connected to the management network CN13. TheSVP 170 can also be connected to the management server 20 and host 10via the LAN interface 180. Hence the management server 20 and host 10can acquire information for the storage control apparatus 100 and managethe storage control apparatus 100 via the management network CN13. Whenmanaging the storage control apparatus 100 from the host 10, amanagement program is installed on the host 10 in advance.

The storage section 110 comprises, for example, a plurality of diskdrives 111 connected in an array. The disk drives 111 are equivalent to“storage devices”. The disk drives 111 can be configured as variousstorage devices, such as for example hard disk drives, semiconductormemory drives, optical disc drives, magneto-optical disc drives,magnetic tape drives, and similar.

In the case of hard disk drives, various types of hard disk drives canbe used, such as FC (Fibre Channel) disks, SATA (Serial AT Attachment)disks, and SCSI (Small Computer System Interface) disks. Also, differentstorage devices can coexist within the storage section 110.

For example, a single group may be configured from a prescribed numberof disk drives 111, such as four drives or eight drives. This group iscalled a RAID group (parity group) 112. Each of the disk drives 111 in aRAID group 112 provides a physical storage area, and an aggregate ofthese physical storage areas is formed. Hence a RAID group 112 can becalled a physical storage device. Although there are differencesdepending on the RAID level, of the disk devices 111 in a group 112, oneor a plurality of disk drives 111 is used to store parity data. Asexplained below, an intermediate storage device 112V is provided in aRAID group 112.

Either one or a plurality of logical volumes 113 can be set in thephysical storage area of the RAID group 112. Logical volumes 113 areallocated to communication ports 121 of CHAs 120, and are accessed bythe host 10. Logical volumes 113 may also be called logical storagedevices.

Conceptually, a virtual logical volume (virtual volume) 113 is alsoprovided within the storage section 110, as indicated by the brokenline. However, the physical entity of the virtual volume 113 does notexist within the storage section 110, but exists within the connectiondestination storage control apparatuses 200, 300. The connection sourcestorage control apparatus 100 can incorporate the storage resources ofthe connection destination storage control apparatuses 200, 300 as ifthese were the connection source storage control apparatus' own storageresources by means of the above-described external connection function.Hence the storage control apparatus 100 need not necessarily comprisedisk drives 111, and can be configured as a network switch.

Next, the configuration of the first connection destination storagecontrol apparatus 200 is explained. This connection destination storagecontrol apparatus 200 can be configured as a disk array subsystemcomprising a controller 201 and storage section 210, for example.

The controller 201 controls operation of the connection destinationstorage control apparatus 200, and so similarly to the above-describedcontroller 101, comprises CHA functions, DKA functions, cache memory,shared memory, and similar. The controller 201 is connected to acommunication port 121 of the controller 101 via the communication port221. A communication path P1 is set between the controller 201 and thecontroller 101. Further, the controller 201 is connected to the storagesection 210 via the communication port 231.

Similarly to the above-described storage section 110, the storagesection 210 comprises a plurality of disk drives 211. A RAID group 212is formed by a plurality of disk drives 211. A logical volume (realvolume) 213 is provided in this RAID group 212.

The second connection destination storage control apparatus 300,similarly to the first connection destination storage control apparatus200, can be configured as a disk array subsystem comprising a controller301 and storage section 310.

The controller 301 controls operation of the connection destinationstorage control apparatus 300. The controller 301, similarly to thecontroller 201, comprises CHA functions, DKA functions, cache memory,shared memory, and similar. The controller 301 is connected to thecommunication port 121 of the controller 101 via the communication port321. A communication path P2 is set between the controller 301 and thecontroller 101. The controller 301 is connected to the communicationport 221 of the controller 201 via the communication port 321. Acommunication path P3 is set between the controller 301 and thecontroller 201.

The storage section 310, similarly to the storage section 210, comprisesa plurality of disk drives 311, a RAID group 312 and a logical volume(real volume) 313.

Due to limitations of space, only two connection destination storagecontrol apparatuses are shown; but three or more connection destinationstorage control apparatuses can be provided. Further, by installing anexternal connection function in the connection destination storagecontrol apparatuses as well, a certain connection destination storagecontrol apparatus can be used as a connection origin to connect toanother connection destination storage control apparatus.

Here, normal read command processing and write command processing by aCHA 120 and DKA 130 are first explained. Upon receiving a read commandissued by the host 10, the CHA 120 stores the read command in sharedmemory 150. The DKA 130 references shared memory 150 from time to time.

The DKA 130, upon discovering an unprocessed read command, converts theread address contained in the read command into a physical address of adisk drive 111, and reads data from the prescribed disk drive 111. TheDKA 130 stores the data read from the disk drive 111 in cache memory140. The CHA 120 reads the data stored in cache memory 140, andtransmits the data to the host 10.

Upon receiving a write command issued by the host 10, the CHA 120secures an area to store the write data in cache memory 140, and storesthe write command in shared memory 150. Then, the CHA 120 stores thewrite data received from the host 10 in cache memory 140.

The DKA 130 confirms the write command stored in shared memory 150, andreads the write data from cache memory 140. The DKA 130 performs theabove-described address conversion, and then stores the write data inthe prescribed disk drive 111.

At the time at which the write data is stored in cache memory 140, theCHA 120 can notify the host 10 of the completion of write commandprocessing (asynchronous processing). Or, at the time at which the DKA130 confirms that the write data has been written to the disk drive 111,the CHA 120 can notify the host 10 of the completion of write commandprocessing (synchronous processing).

The above is data input/output processing for a real volume of thestorage control apparatus 100. Next, data input/output processing for avirtual volume is explained. A virtual volume 113 within the connectionsource storage control apparatus 100 is assumed to be associated with areal volume 213 within the first connection destination storage controlapparatus 200.

First, when a write command for the virtual volume has been issued, theCHA 120 converts the volume identifier and address of the read commandinto those for the real volume 213, and transmits the read command tothe connection destination storage control apparatus 200. The connectiondestination storage control apparatus 200 reads data from the realvolume 213 according to the read command, and transmits the read-outdata to the connection source storage control apparatus 100. The CHA120, upon receiving data from the connection destination storage controlapparatus 200, causes this data to be stored in cache memory 140. TheCHA 120 then transmits the data stored in cache memory 140 to the host10.

When a write command is issued for a virtual volume, the CHA 120converts the volume identifier and address for the write command intothose for the real volume 213. The CHA 120 then causes the write datareceived from the host 10 to be stored in cache memory 140. The CHA 120transmits the write command and write data to the connection destinationstorage control apparatus 200. The connection destination storagecontrol apparatus 200 stores the write data received from the connectionsource storage control apparatus 100 in the real volume 213.

FIG. 4 is an explanatory diagram which schematically shows the storageconfiguration of the storage system. The connection source storagecontrol apparatus 100 can comprise a plurality of logical volumes 113.The logical volumes can be broadly divided into real volumes and virtualvolumes. In FIG. 4, real volumes indicated by solid lines aredistinguished by “R-LU”, and virtual volumes indicated by broken linesare indicated by “V-LU”.

Each logical volume 113 is connected to an intermediate storage device(VDEV) 112V, regardless of whether the volume is a real volume or avirtual volume.

An intermediate storage device 112V corresponds to a RAID group 112.However, an intermediate storage device 112V not accompanied by aphysical entity is a virtual intermediate storage device, and exists incache memory 140. An intermediate storage device not accompanied by aphysical entity is a device not linked to a disk drive 111 in theconnection source storage control apparatus 100, that is, a device inwhich a virtual volume is provided.

These virtual intermediate storage devices (VDEV#12, VDEV#13, VDEV#14)112V are ultimately associated with one of the real volumes. In FIG. 4,the intermediate storage devices 112V indicated by “VDEV#12, VDEV#13”are associated, respectively, with the real volume (R-LU#21) 213 of thefirst connection destination storage control apparatus 200, and with thereal volume (R-LU#22) 213 of the first connection destination storagecontrol apparatus 200 and the real volume (R-LU#31) 313 of the secondconnection destination storage control apparatus 300.

The intermediate storage device 112V indicated as “VDEV#14” is connectedto a real volume (R-LU#32) in the second connection destination storagecontrol apparatus 300 via the virtual volume (V-LU#23) 213 of the firstconnection destination storage control apparatus 200. In this way,virtual volumes provided to the host 10 can be associated with a realvolume via another virtual volume.

Similarly to the storage hierarchy of the connection source storagecontrol apparatus 100, each of the connection destination storagecontrol apparatuses 200, 300 also can comprise a physical storage layer(disk drives 211, 311), an intermediate storage layer (212V, 312V)obtained by virtualizing the physical storage layer, and a logicalstorage layer (213, 313) provided so as to remove portions of thestorage area of the intermediate storage layer.

The configuration shown in FIG. 4 is merely an example used forillustration, and other configurations are possible. For example, anintermediate storage device can be provided in a single disk drive. Or,a plurality of logical volumes can be configured from a singleintermediate storage device; or, a single logical volume can beconfigured from a plurality of intermediate storage devices.

FIG. 5 is an explanatory diagram showing a volume management table T1 tomanage logical volumes within the storage system. This volume managementtable T1 can be stored in the shared memory 150 of the connection sourcestorage control apparatus 100. Also, all of or a portion of the table T1can be copied to local memory in each of the CHAs 120. This table T1 canalso be copied to the connection destination storage control apparatuses200, 300, and so can be shared among all the storage controlapparatuses.

The volume management table T1 associates and manages, for example,volume numbers, volume sizes, intermediate storage device numbers,intermediate storage device sizes, device types, apparatus numbers, andaddress information. As is similarly the case in the followingexplanation, volume numbers in the drawings are values set in eachdiagram as convenient for purposes of explanation, and are not mutuallyrelated.

In the storage system, a volume number (with “number” abbreviated to “#”in the figure) is identifying information which is uniquely assigned toeach logical volume in the storage system. The volume size is thestorage capacity of the logical volume. The intermediate storage devicenumber is information used to identify the intermediate storage device(VDEV) in which the logical volume is provided. The intermediate storagedevice size is the storage capacity of the intermediate storage device.The device type is information indicating the type of physical entity(disk drive) associated with the intermediate storage device. Theapparatus number is information used to identify the storage controlapparatus having the data storage location (that is, the disk drive andreal volume) of the logical volume. Address information is informationused to access the data storage location of the logical volume.

Real volumes within the connection source storage control apparatus 100are associated with disk drives 111 within the connection source storagecontrol apparatus 100. Hence in a real volume in the storage controlapparatus 100, a drive number list to identify associated disk drives111 is set in the address information. On the other hand, a virtualvolume within the connection source storage control apparatus 100 isassociated with real volumes 213, 313 within the connection destinationstorage control apparatuses 200, 300. Hence communication pathinformation to access associated external real volumes is set, asaddress information, in virtual volumes in the storage control apparatus100.

Here, a real volume existing outside the connection source storagecontrol apparatus 100, that is, real volumes 213, 213 of the connectiondestination storage control apparatuses 200, 300, are called externalvolumes, and real volumes 113 existing within the connection sourcestorage control apparatus 100 can be called internal volumes. Addressinformation (communication path information) set in the virtual volumeswithin the connection source storage control apparatus 100 can contain,for example, an external volume LUN (Logical Unit Number), a WWN, orsimilar.

The configuration of the volume management table T1 is not limited tothat shown in FIG. 5. It is sufficient that the table containinformation enabling identification of the relations between each of thelogical volumes 113 in the connection source storage control apparatus100 and the disk drives 111 or external volumes 213, 313 correspondingto these logical volumes 113.

Further, a volume status management table or similar to manage thevarious state of logical volumes can also be prepared, separately fromthe volume management table T1. In such a management table, informationon volumes forming copy pairs, free space, and other information ismanaged.

FIG. 6 is an explanatory diagram showing a function management table T2used to manage functions which can be used by each of the storagecontrol apparatuses 100, 200, 300. This management table T2 can forexample be stored in the shared memory 150 of the connection sourcestorage control apparatus 100.

The function management table T2 can be configured so as to associateeach apparatus number, for example, with one or a plurality of supportedfunctions. A supported function is a function which can be utilizedwithin a storage control apparatus. Supported functions registered inthe management table T2 may be equivalent to all the functions of thestorage control apparatus; or, only a portion of the functions of astorage control apparatus may be registered in the management table T2as a supported function.

As explained below, the user can, via the management server 20 orsimilar, select functions which can be executed by the storage controlapparatuses 100, 200, 300. That is, of all the functions provided in thestorage control apparatuses, the user can select an arbitrary function,and can cause only this selected function to be registered in themanagement table T2 as a function which can be executed within each ofthe storage control apparatuses.

FIG. 7 is an explanatory diagram showing a function executing apparatusmanagement table T3, to manage the apparatus executing functions forwhich there has been an execution function from the host 10. Thismanagement table T3 can be stored in the shared memory 150 of theconnection source storage control apparatus 100, similarly to the tablesT1 and T2.

The function executing apparatus management table T3 is configured tocomprise individual function executing apparatus management tables T31to T33, to individually manage executing apparatuses for each function.For example, table T31 manages information regarding which storagecontrol apparatus will execute the local volume copy function. Table T32manages information regarding which storage control apparatus executesthe encryption function. And table T33 manages information regardingwhich storage control apparatus executes the compression function.

The function executing apparatus management tables T31 to T33 areconfigured so as to associate, for example, information to identify avolume to which an executed function is applied (volume numbers),information to identify an executing apparatus (apparatus number), andconditions for execution of the function (execution conditions).Execution conditions are further explained below.

Focusing on the table T31 which manages the executing apparatus for thelocal volume copy function, this table T31 associates and manages copysource volume numbers, copy destination volume numbers, executingapparatus numbers, and execution conditions. Here, as indicated in thefinal row of the table T31, local volume copying may in some cases byrealized through remote copying. For example, when the physical entities(real volumes) of the copy source volume and the copy destination volumeare distributed in the connection destination storage controlapparatuses 200 and 300, the remote copy function between the connectiondestination storage control apparatuses 200 and 300 is used toaccomplish copying between virtual volumes.

The table T32 to manage the executing apparatus for the encryptionfunction, and the table T33 to manage the executing apparatus for thecompression function, also are configured to contain informationidentifying the range of volumes to which the functions can be applied,information to identify the storage control apparatus which is toexecute the function, and execution conditions.

Execution conditions are explained. As stated above, executionconditions are startup conditions for execution of the function.Execution conditions may be set so as to stipulate, for example, “None”;“when the storage control apparatus of the origin of the executionrequest (the connection source storage control apparatus) has a loadexceeding a prescribed threshold”; “when the storage control apparatusof the destination of the execution request (a connection destinationstorage control apparatus) has a load less than a prescribed threshold”;“when the storage control apparatus of the origin of the executionrequest has a load equal to or greater than a prescribed threshold, andmoreover the storage control apparatus of the destination of theexecution request has a load less than a different prescribedthreshold”; and similar.

A function for which “None” is stipulated as the execution condition canbe executed unconditionally by a storage control apparatus registered asan executing apparatus. A function for which the relation between athreshold and the current load is registered as an execution conditioncan be executed by a storage control apparatus registered as anexecuting apparatus only when this condition is satisfied.

Here, execution conditions can also be defined in terms of conditionsother than loads. For example, execution conditions such as, “executionis permitted only when the time required for function execution iswithin a time frame specified in advance”, or “execution is permittedwhen the host requesting the function execution is a host specified inadvance”, can also be set. Execution conditions can also be set incombination with time frames, originating host numbers, and load state.

The configuration of the function executing apparatus management tableT3 is not limited to that shown in FIG. 7. For example, management canbe performed in units of logical volumes, as shown in FIG. 7; or,management of the apparatuses executing functions can be performed inunits of blocks within volumes. Or, a plurality of volumes can begrouped together and managed, with the apparatuses for functionexecution managed in group units. Function execution apparatuses canalso be managed in units of the storage control apparatus. Or,configurations are possible which set values for each function indifferent management units (volume units, block units, group units, orsimilar).

FIG. 8 shows an example of a user interface provided to users. Thewindows G1 and G2 shown in FIG. 8 display, for example, the windows ofthe management server 20 and management terminal 31. In the top half ofFIG. 8 is shown the window G1, enabling the user to select functions foruse by each storage control apparatus.

This window G1 can comprise, for example, an apparatus-numberspecification section G11, function display section G12, use settingsection G13, execution condition setting section G14, registrationbutton B11, and cancellation button B12.

The apparatus number specification section G11 is used to select one ofthe storage control apparatuses 100, 200, 300. The function displaysection G12 lists the names of all the functions of a selected storagecontrol apparatus. The use setting section G13 is used to selectfunctions to be used (functions planned for execution) among thedisplayed function names. The execution condition setting section G14sets the conditions for execution of a selected function. In the figure,in order to show the values which can be taken in the use settingsection G13, an example is shown in which the first connectiondestination storage control apparatus 200 does not use the local volumecopy function. Further, due to limitations of space the display detailsof the execution condition setting section G14 are simplified.

In the lower half of FIG. 8 is shown a window G2 used to set the storagecontrol apparatus for execution of functions selected by the user. Thiswindow G2 can comprise, for example, a function name selection sectionG21, execution volume display section G22, executing apparatus numbersetting section G23, registration button B21, and cancellation buttonB22.

The function name selection section G21 is used to select any of thefunctions from among those registered on the window G1. The executionvolume display section G22 displays volume numbers to which a selectedfunction is applied. The executing apparatus number setting section G23sets the storage control apparatus to be used when executing a functionfor the volume in question.

The user interface shown in FIG. 8 is one example, and others arepossible. The windows G1 and G2 can be combined into a single window, orthe windows G1 and G2 can each comprise a plurality of windows. Further,each of the windwos G1 and G2 can comprise elements (display fields,setting fields, and similar) other than those shown in FIG. 8.

Next, operation to allocate appropriate storage control apparatuses tofunction execution is explained, referring to FIG. 9 and FIG. 10. FIG. 9is a flowchart of allocation of an apparatus for function execution;FIG. 10 is a flowchart showing the details of the allotment processing(S13) in FIG. 9. In the following explanation, steps are abbreviated to“S”. Further, and similarly in the subsequent explanations, eachflowchart is created only to the extent necessary to understand andimplement the invention, and differs from an actual computer program.This processing is executed by the controller 101 of the connectionsource storage control apparatus 100.

The controller 101 is instructed by the host 10 to execute a prescribedfunction (S11). A prescribed function is a function registered as asupported function. The host 10, by issuing a prescribed commandcontaining information to identify the volume and the function forexecution, requests execution of the prescribed function.

Here, the host 10 can request execution of a prescribed function bytransmitting a prescribed command to the controller 101 via the I/Ocommunication network CN11. For example, a command issued from the host10 can be received directly by the controller 101 and processed; or, thecommand can be processed after first storing the command in a dedicatedlogical volume (also called a command device) for receiving commands.Further, the host 10 can also issue a request to the controller 101 toexecute a prescribed function via the management communication networkCN13.

Upon receiving a request for execution of a prescribed function from thehost 10, the controller 101 judges whether the prescribed function canbe executed by the connection source storage control apparatus 100(S12). If the connection source storage control apparatus 100 canexecute the prescribed function (S12: YES), the allotment processingshown in FIG. 10 is performed (S13). This allotment processing isperformed to allot execution of prescribed functions requested by thehost 10 among the connection source storage control apparatus 100 andthe connection destination storage control apparatuses 200, 300. Theallotment processing is further explained below in conjunction with FIG.10.

If the prescribed function cannot be executed by the connection sourcestorage control apparatus 100 (S12: NO), the controller 101 searches theexternal real volumes 212, 313 associated with the volume 113 for whichthe prescribed function is to be executed (S14). This search isperformed by referencing the volume management table T1.

The controller 101 judges whether an external real volume 213, 313 isassociated with the volume 113 for which the prescribed function is tobe executed (S15). If an external real volume is not associated with thevolume 113 in question (S15: NO), the controller 101 notifies the host10 of an error (S16). For example, this is the case when the volume forwhich the prescribed function is to be executed is a real volume withthe storage control apparatus 100, and moreover the prescribed functioncannot be executed by the storage control apparatus 100. In such a case,the controller 101 notifies the host 10 that the requested prescribedfunction cannot be executed.

On the other hand, if the volume 113 for which the prescribed functionis to be executed is a virtual volume, and is associated with one of theexternal real volumes 213, 313 (S15: YES), the controller 101 identifiesthe connection destination storage control apparatus having theassociated real volume (S17). The volume management table T1 or thefunction executing apparatus management table T3 can be used for thisidentification.

Next, the controller 101 references the function management table T2,and judges whether the identified connection destination storage controlapparatus (200 or 300) can execute the prescribed function (S18). If theidentified connection destination storage control apparatus cannotexecute the prescribed function (S18: NO), the controller 101 notifiesthe host 10 of an error (S24).

If the identified connection destination storage control apparatus canexecute the prescribed function (S18: YES), the controller 101 acquiresthe state of the identified connection destination storage controlapparatus (S19). Various methods can be used to acquire the state of theconnection destination storage control apparatus.

For example, the controller 101 can issue a query command to thecontroller of the connection destination storage control apparatus, toquery the load and other state parameters, and can detect the state ofthe connection destination storage control apparatus through theresponse to this command. Or, each of the connection destination storagecontrol apparatuses 200, 300 can, either regularly or irregularly,notify the connection source storage control apparatus 100 of their ownstate. Or, each of the storage control apparatuses 100, 200, 300 cannotify a management server 20 of their own state, and the managementserver 20 can manage the state of each of the storage controlapparatuses. In this case, the controller 101 can query the managementserver 20 to acquire the state of the connection destination storagecontrol apparatus registered as the executing apparatus.

Next, the controller 101 judges whether the execution conditions set forthe prescribed function, execution of which has been requested by thehost 10, are satisfied (S20). That is, the controller 101 judges whetherthe state of the connection destination storage control apparatusregistered as the executing apparatus satisfies the executionconditions. If the execution conditions are not satisfied (S20: NO), theprescribed function cannot be executed, and so the controller 101notifies the host 10 of an error (S24).

If the execution conditions are satisfied (S20: YES), the controller 101instructs the connection destination storage control apparatusregistered as the executing apparatus to execute the prescribed function(S21). The controller 101 converts the instruction details from the host10 as appropriate and transmits the result to the connection destinationstorage control apparatus so as to obtain the result expected by thehost 10.

The controller 101 then waits for notification of the completion ofprocessing from the connection destination storage control apparatuswhich has been instructed to execute the prescribed function (S22). Iffor example a notification of processing completion has not arrived fromthe connection destination storage control apparatus within a prescribedtime, set in advance (S22: NO), the controller 101 judges that theprescribed function has not been executed normally, and notifies thehost 10 of an error (S24).

If notification indicating that processing has been completed normallyis received from the connection destination storage control apparatuswhich has been requested to execute the prescribed function (S22: YES),the controller 101 notifies the host 10 of the normal completion ofexecution of the prescribed function (S23).

A configuration is also possible in which, at the time at which theconnection destination storage control apparatus is instructed toexecute the prescribed function (S21), the host 10 is notified of thecompletion of processing without waiting for reception of notificationof the completion of processing from the connection destination storagecontrol apparatus.

The allotment processing of S13 in FIG. 9 is explained, referring toFIG. 10. The controller 101 searches for external real volumesassociated with the volumes to which the prescribed function is applied(S1300). The controller 101 judges whether an external real volume isassociated with the volume to which the function is applied (S1301).

If no external real volumes are associated with the volume (S1301: NO),that is, if the volume in question is a real volume within theconnection source storage control apparatus 100, the controller 101executes the prescribed function (S1302). That is, the prescribedfunction requested by the host 10 is executed within the connectionsource storage control apparatus 100 for the real volume in question.The controller 101 then notifies the host 10 of the normal completion ofprocessing (S1303).

If on the other hand the volume to which the prescribed function is tobe applied is a virtual volume (S1301: YES), the controller 101identifies the connection destination storage control apparatus havingthe external real volume associated with the virtual volume (S1304).

The controller 101 then executes steps similarly to those described inS18 to S23 in FIG. 9. That is, if the controller 101 judges that theidentified connection destination storage control apparatus can executethe prescribed function (S1305: YES), the state of the connectiondestination storage control apparatus is acquired (S1306).

The controller 101 compares the execution conditions set in advance forthe prescribed function execution of which has been requested by thehost 10 with the state of the connection destination storage controlapparatus, and judges whether the execution conditions are satisfied(S1307). If the execution conditions are satisfied (S1307: YES), thecontroller 101 instructs the connection destination storage controlapparatus to execute the prescribed function (S1308).

Upon receiving processing completion notification from the connectiondestination storage control apparatus (S1309: YES), the controller 101notifies the host 10 that the prescribed function has been appliednormally to the volume in question (S1310).

Similarly to the explanation of FIG. 9, when the identified connectiondestination storage control apparatus is not provided with theprescribed function (S1305: NO), when the execution conditions for theprescribed function are not satisfied (S1307: NO), and when processingcompletion notification is not received from the connection destinationstorage control apparatus instructed to execute the prescribed function(S1309: NO), the controller 101 notifies the host 10 of an error(S1311).

The instruction to execute the prescribed function may be from themanagement server 20 or management terminal 31 as well as from the host10.

By means of the above-described configuration, this embodiment has thefollowing advantageous results. In this embodiment, even when a functionis not provided in the connection source storage control apparatus 100,if the function is provided in the connection destination storagecontrol apparatuses 200, 300, then execution of the function can berequested of a connection destination storage control apparatus capableof execution. Hence even requests for functions, which can be executedonly by the connection destination storage control apparatuses 200, 300,can be accepted by and processed by the connection source storagecontrol apparatus 100 by accepting requests from the host 10. As aresult, the functionality of the connection source storage controlapparatus 100, as seen from the host 10, can be enhanced. In otherwords, the functions of the connection source storage control apparatus100, which is the interface for processing of the storage system, can beexpanded in virtual form.

Hence in a storage system in which connection destination storagecontrol apparatuses 200 and 300 each with unique characteristicscoexist, even if the connection source storage control apparatus 100serving as interface is not provided with a portion of or all of suchfunctions, all of these characteristic functions can be caused to beexecuted, so that convenience of use is enhanced.

In this embodiment, a judgment is made as to whether a connectiondestination storage control apparatus 200 and 300 registered as anexecuting apparatus should be instructed to execute a prescribedfunction execution of which has been requested by the host 10, based onthe details of the prescribed function and on the state of theconnection destination storage control apparatuses registered asexecuting apparatuses. That is, if a connection destination storagecontrol apparatus registered as an executing apparatus satisfies theexecution conditions, the apparatus is instructed to execute theprescribed function. Hence the loads on connection destination storagecontrol apparatuses can be prevented from becoming excessive, and loadscan be distributed appropriately.

In this embodiment, functions which can be used are registered inadvance for each storage control apparatus, and moreover a configurationis employed in which executing apparatuses can be set in advance foreach function registered as a function which can be used. Hence loadscan be distributed in function units, for improved convenience of use.Further, usable functions can be set for each storage control apparatus,so that task allotment among each of the storage control apparatuses100, 200, 300 is possible.

Embodiment 2

Next, a second embodiment is explained using FIG. 11 through FIG. 14.Each of the following embodiments, including this embodiment, isequivalent to a modified example of the first embodiment. In each of thefollowing embodiments, explanations of components which are redundantwith above-described components are omitted, and explanations centermainly on characteristic portions. In this embodiment, a case isexplained in which a compression function (including both compressionand expansion) is used in each of the storage control apparatuses 100,200, 300.

FIG. 11 is an explanatory diagram showing the overall configuration ofthe storage system of this embodiment. Each of the storage controlapparatuses 100, 200, 300 is provided with a compression section and anexpansion section. The connection source storage control apparatus 100comprises a compression section 102 and an expansion section 103.Similarly, the first connection destination storage control apparatus200 comprises a compression section 202 and an expansion section 203.The second connection destination storage control apparatus 300comprises a compression section 302 and an expansion section 303.

The compression sections 102, 202, 302 compress input data according toa prescribed compression algorithm and output the compressed data. Theexpansion sections 103, 203, 303 restore input compressed data to thestate prior to compression based on the compression algorithm used tocompress the data, and output the result.

These compression sections 102, 202, 302 and expansion sections 103,203, 303 can for example be configured as ASICs (Application-SpecificIntegrated Circuits) or other hardware circuits. Or, the compressionsections 102, 202, 302 and expansion sections 103, 203, 303 can beconfigured as computer programs, and the computer programs can be readand executed by a CPU within the controller. Also, the compressionsections can be configured as hardware circuits, and the expansionsections can be configured as computer programs.

FIG. 12 is an explanatory diagram showing an example of variousmanagement information used to execute the compression function withinthe storage system. In the upper part of FIG. 12 is shown managementinformation held by each of the storage control apparatuses 100, 200,300; in the lower part of FIG. 12 are shown details of the managementinformation. The tables T1 to T3 described in the above embodiment arealso provided in the connection source storage control apparatus 100,but are omitted from FIG. 12.

The connection source storage control apparatus 100 holds a compressionfunction setting management table T4, compression state management tableT5, and compression management information T6. Each of the connectiondestination storage control apparatuses 200, 300 holds a compressionfunction setting management table T4 and compression managementinformation T6.

The compression function setting management table T4 is a table to set,for each volume, the execution mode of the compression function. Thetable T4 is configured so as to associate, for example, the volumenumber of a volume for application of the compression function, acompression execution setting to set whether to perform compression, anexpansion execution setting to set whether to perform expansion, and acompression algorithm to be used.

Either “compress” or “not compress” values are set for each compressionexecution setting. When a “compress” value is set, the compressionsection performs compression. In this case, the compression sectioncompresses the input data and outputs the result. That is, the storagecontrol apparatus compresses the received data and stores the result inthe volume. When “not compress” is set, the compression section does notperform compression. In this case, the input data is output as-is,without modification. That is, the storage control apparatus stores thereceived data in the volume as-is, without performing compression.

Either “expand” or “not expand” values are set for expansion executionsettings. When “expand” is set, the expansion section performsexpansion. In this case, the storage control apparatus expands data readfrom the volume and transfers the data. When “not expand” is set, theexpansion section does not perform expansion. In this case, the inputdata is output as-is, without modification. In other words, the storagecontrol apparatus transfers the data read from the volume as-is.

As compression algorithms, for example, the run-length algorithm,Huffman algorithm, or various other well-known compression algorithmscan be used.

The compression state management table T5 manages the compression stateof each volume. This table T5 is configured to associate, for example,volume numbers, compression state, and compression algorithms. Either“compressed” or “uncompressed” is set as the value of the compressionstate. A volume set as “compressed” stores compressed data; a volume setas “uncompressed” stores data which has not been compressed.

The compression management information T6 manages various informationwhich changes with compression. The compression management informationT6 can associate, for example, volume numbers, addresses prior tocompression, addresses after compression, and compression algorithms. Byreferencing the compression management information T6, the storagecontrol apparatus (controller) can accommodate read and write requestsfor compressed data.

In this embodiment, a configuration is employed in which the compressionmanagement information T6 is common to all of the storage controlapparatuses 100, 200, 300. Hence the storage control apparatus which isto execute compression or expansion can be switched.

Next, execution of compression and expansion is explained. Here, anexample is explained in which only the connection source storage controlapparatus 100 executes compression and expansion. FIG. 13 is a flowchartshowing compression. In this flowchart, write data to be written to avirtual volume is compressed by the connection source storage controlapparatus 100 (controller 101), and the compressed data is stored in areal volume 213 of a connection destination storage control apparatus(here assumed to be the first connection destination storage controlapparatus 200).

First, the controller 101 sets the execution mode for the compressionfunction of the connection destination storage control apparatus 200 to“not compress” and “not expand” (S31, S32). That is, data compressionfunctions are disabled in the controller 201.

In this state, upon receiving the write data from the host 10 (S33), thecontroller 101 stores the write data in cache memory 140 (S34), andnotifies the host 10 of the completion of write command processing(S35). As explained above, there are synchronous and asynchronousmethods of write command processing. Hence a configuration may also beemployed in which the host 10 is notified of the completion of writecommand processing after confirmation that the write data has beenstored by the connection destination storage control apparatus 200.

The controller 101 issues a write command to the connection destinationstorage control apparatus 200, explicitly stating the real volume 213for data storage (S36). The controller 201 of the connection destinationstorage control apparatus 200, upon receiving the write command, securesa cache area to store the write data (S37).

The controller 101 uses the compression section 102 to compress thewrite data (S38), and transmits the compressed write data to thecontroller 201 (S39). The controller 201 receives the compressed writedata (S40), and stores the compressed write data in cache memory or inthe real volume 213 (S41).

Here, because compression is disabled in the connection destinationstorage control apparatus 200, the controller 201 stores the compressedwrite data received from the controller 101 in the real volume 213as-is. The controller 201, after storing the compressed write data incache memory, can with appropriate timing cause the data to be stored indisk drives 211 of the real volume 213.

The controller 101 then updates address information and similar of thecompression management information T6 (S42). The controller 201 alsoupdates compression management information T6 (S43). For example, eachtime compressed data is received, the controller 201 can query thecontroller 101 for updated compression management information T6, toupdate the compression management information T6 within the controller201. Or, the controller 101 can notify the controller 201 of the updatedportions of the compression management information T6. A configurationmay also be employed in which a volume for management data to be used incommon by a plurality of storage control apparatuses is provided, andcompression management information T6 is stored within this volume formanagement information. A configuration is also possible in which amanagement server 20 or similar manages the compression managementinformation T6 in a unified manner.

FIG. 14 is a flowchart showing expansion. The controller 101, uponreceiving from the host 10 a read command requesting data reading from avirtual volume (S51), issues a separate read command to the connectiondestination storage control apparatus 200 (S52). This read commandcontains information to access the real volume 213 which actually storesthe compressed data, the read address, and similar. The controller 101can reference the compression management information T6 to cause thedata requested by the host 10 to be read from the real volume 213.

The controller 201 of the connection destination storage controlapparatus 200, upon receiving a read command from the controller 101(S53), secures a cache area for temporary storage of data, and reads thecompressed data from the disk drive 211 corresponding to the real volume213 (S54). After storing the compressed data in cache memory, thecontroller 201 transmits the compressed data to the controller 101(S55). Here, because expansion is disabled in the connection destinationstorage control apparatus 200, the compressed data is read in thecompressed state from the disk drive 211 and transmitted to thecontroller 101.

Upon receiving the compressed data from the controller 201 (S56), thecontroller 101 expands the compressed data (S57), and transmits theexpanded data to the host 10 (S58).

In this embodiment configured as described above also, advantageousresults similar to those of the first embodiment are obtained. Inaddition, in this embodiment each of the storage control apparatuses100, 200, 300 is provided with a common compression function, and theexecution mode of the compression function can be set in each case asappropriate. Hence the user can freely set values to perform compressionor expansion in any of the storage control apparatuses, so that loaddistribution is possible, and user convenience is improved.

Embodiment 3

A third embodiment is explained using FIG. 15 through FIG. 17. In thisembodiment, only one connection destination storage control apparatushas a compression function; this compression function is used tocompress the data of a copy source volume and store the result in a copydestination volume.

FIG. 15 is an explanatory diagram showing the overall configuration ofthe storage system of this embodiment. For convenience of explanation,in the following the connection destination storage control apparatusprovided with a compression function (a compression section andexpansion section) is assumed to be the first connection destinationstorage control apparatus 200. The copy source volume V1 a is assumed tobe a real volume of the connection source storage control apparatus 100,and the copy destination volume V1 c is assumed to be a virtual volumeassociated with a real volume V3 c of the second connection destinationstorage control apparatus 300.

As shown in FIG. 15, the connection source storage control apparatus 100comprises the copy source volume V1 a, a relay volume V1 b forcompression, and the copy destination volume V1 c. The copy sourcevolume V1 a is a real volume within the storage control apparatus 100.The relay volume V1 b is a virtual volume, associated with a real volumeV2 b of the first connection destination storage control apparatus 200.The copy destination volume V1 c is a virtual volume, associated with areal volume V3 c of the second connection destination storage controlapparatus 300. Only the first connection destination storage controlapparatus 200 is provided with a compression section 202 and expansionsection 203.

The above premises are for convenience of explanation, and others may beused. For example, if the copy source volume V1 a and copy destinationvolume V1 c are volumes recognized by the host 10, then they can existanywhere. It is sufficient that the physical entity (real volume) of avolume for compression exist in a storage control apparatus 200 having acompression function.

FIG. 16 is a flowchart showing processing when data is compressed andwritten from a copy source volume V1 a to a copy destination volume V1c. The controller 101 receives, from the host 10 or from the managementserver 20 or management terminal 31, a compression copy request with thecontents, “compress the data of copy source volume V1 a, via compressionrelay volume V1 b, and store the result in copy destination volume V1 c”(S61).

The controller 101 sets the compression function of the controller 201to “compress” and “not expand” (S62, S63). That is, in the controller201, compression is enabled, and expansion is disabled.

The controller 101 issues a compression copy request to the controller201 having the compression function (S64), and reads data from the copysource volume V1 a (S65). Then, the controller 101 transmits the dataread from the copy source volume V1 a to the controller 201 (S67).

The controller 201, upon receiving data from the controller 101 (S68),compresses the received data (S69), and causes the compressed data to bestored in the real volume V2 b associated with the relay volume V1 b(S70). This real volume V2 b is also called a real volume forcompression.

The controller 201 then notifies the controller 101 of the completion ofcompression and storage of the received data (S71). Upon receiving thisnotification, the controller 101 sets the compression state of thecompression volume V1 b in the compression state management table T5 to“compressed” (S72).

The controller 201 issues a write command to the controller 301 of thesecond connection destination storage control apparatus 300 (S73). Uponreceiving the write command from the controller 201 (S74), thecontroller 301 secures a cache area to receive the write data.

The controller 201 reads the compressed data stored in the real volumefor compression V2 b (S75), and transmits the compressed data to thecontroller 301 (S76). The controller 301, upon receiving the compresseddata (S77), causes the compressed data to be stored in the real volumeV3 c associated with the copy destination volume V1 c (S78).

Upon completing transmission of the compressed data to the controller301, the controller 201 notifies the controller 101 of the completion ofcompressed data copying (S79). Upon receiving this notification, thecontroller 101 notifies the host 10 of the completion of compressioncopying (S80), and sets the compressed state of the copy destinationvolume V1 c in the compression state management table T5 to “compressed”(S81).

The controller 201 then transmits compression management information T6,reflecting the completion of the compression copy processing, to thecontroller 101 (S82). The controller 101 then updates the compressionmanagement information T6 which it itself manages (S83).

The compression management information T6 need not necessarily bemanaged by the connection source storage control apparatus 100(controller 101), but may be managed by the second connectiondestination storage control apparatus 300 having the copy destinationvolume. Or, the compression management information T6 may be managed bythe first connection destination storage control apparatus 200 havingthe compression function, or may be managed by a management server 20.The compression management information T6 is necessary in order toprocess read commands and write commands from the host 10 for compresseddata.

FIG. 17 is a flowchart showing expansion copy processing. In thisprocessing, in a process opposite that of the compression copyprocessing of FIG. 16, compressed data stored in the volume V1 c isexpanded and copied to the volume V1 a. Hence in this processing thecopy source volume is V1 c, and the copy destination volume is V1 a.

The controller 101 receives an expansion copy request from the host 10,the management server 20 or similar, with the contents “expand the data(compressed data) stored in the copy source volume V1 c, via the relayvolume for expansion V1 b, and store the data in the copy destinationvolume V1 a” (S91). The controller 101, upon receiving the expansioncopy request, sets the compression function of the controller 201 to“not compress” and “expand” (S92). By this means, the compressionsection 202 is disabled and the expansion section 203 is enabled in thecontroller 201 (S93).

Next, the controller 101 transmits the compression managementinformation T6 to the controller 201 (S94), and causes the controller201 to store the compression management information T6 (S95). When thecompression management information T6 is managed by the firstconnection-destination storage control apparatus 200 (controller 201),S94 and S95 can be omitted. When the compression management informationT6 is managed by the management server 20 or another external system,the system must be queried.

When these preparations for expansion copying have been completed, thecontroller 101 issues an expansion copy request to the controller 201(S96). Upon receiving the expansion copy request (S97), the controller201 issues a read command to the controller 301 of the second connectiondestination storage control apparatus 300 (S98).

Upon receiving the read command from the controller 201 (S99), thecontroller 301 reads compressed data from the copy source volume V3 c(S100), and transmits the compressed data to the controller 201 (S101).

Upon receiving the compressed data from the controller 301 (S102), thecontroller 201 stores the compressed data as-is, without performingcompression, in the real volume for relay V2 b (S103). The controller201 then notifies the controller 101 of the completion of compresseddata storage (S104). Upon receiving this notification, the controller101 sets the compressed state of the relay volume V1 b in thecompression state management table T5 to “compressed” (S105).

Next, the controller 201 issues a write command to the controller 101(S106). Upon receiving the write command from the controller 201 (S107),the controller 101 secures an area in cache memory 140 for storage ofthe data received from the controller 201. Data transfer may also berealized by means of a read command from controller 101 to controller201.

The controller 201 reads the compressed data from the real volume forrelay V2 b (S108), and causes this compressed data to be expanded(S109). The controller 201 then transmits the expanded data to thecontroller 101 (S110). The compressed data may be expanded whilereading, or the compressed data may all be read first and then expanded.

Upon receiving the expanded data from the controller 201 (S111), thecontroller 101 causes the expanded data to be stored in the copydestination volume V1 a (S112). The controller 101 then sets thecompressed state of the copy destination volume V1 a in the compressionstate management table T5 to “uncompressed” (S113).

The controller 101 notifies the host 10 of the completion of expansioncopy processing (S114), and causes the compression managementinformation T6 to be updated (S115). Similarly to the aboveexplanations, the compression management information T6 can also bemanaged by the controller 201 or similar.

This embodiment, configured as described above, also providesadvantageous results similar to those of the above first embodiment. Inaddition, according to this embodiment when only a single storagecontrol apparatus 200 in the storage system is provided with acompression function, this compression function can be used effectivelyto copy and move volume data, for improved convenience of use.

Further, when a plurality of storage control apparatuses are eachprovided with compression functions, for example only the compressionfunction of a storage control apparatus 200 with small storage capacitymay be enabled, so that compression. and expansion are concentrated in asingle storage control apparatus. By this means, the processingperformance of a storage control apparatus 200 with a small amount offree storage space can be utilized effectively.

And, even when there is little free storage space in the storage controlapparatus 200 having a compression function, by saving compressed datato a storage area of another storage control apparatus 300, the amountof free storage area of the storage control apparatus 200 with thecompression function can be decreased.

Embodiment 4

A fourth embodiment is explained using FIG. 18 and FIG. 19. In thisembodiment, a request to execute a function is issued from theconnection source storage control apparatus 100 to the second connectiondestination storage control apparatus 300, via the first connectiondestination storage control apparatus 200.

FIG. 18 is an explanatory diagram showing the overall configuration ofthe storage system of this embodiment. In this embodiment, the virtualvolumes V1 a, V1 b within the connection source storage controlapparatus 100 are associated with the real volumes V3 a, V3 b within thesecond connection destination storage control apparatus 300, via thevirtual volumes V2 a, V2 b within the first connection destinationstorage control apparatus 200. And, the second connection destinationstorage control apparatus 300 is provided with a local volume copyfunction F21 and a drive power management function F22. The drive powermanagement function F22 is a function for turning on and off the powersupply of disk drives 311 and for making transitions into a low powerconsumption mode (standby mode).

FIG. 19 is a flowchart showing operation of the storage system. The host10 issues an instruction for volume copying between the virtual volumesV1 a and V1 b, or for power management of the disk drives 311 of thevirtual volumes V1 a and V1 b (S121). In the following explanation, thevolume copy function F21 and drive power management function F22 may becalled prescribed functions.

Upon receiving an instruction for execution of a prescribed functionfrom the host 10 (S122), the controller 101 of the connection sourcestorage control apparatus 100 executes the executing apparatusallocation processing described in conjunction with FIG. 9 (S123).Because the controller 101 cannot itself execute the prescribed functionrequested by the host 10, it transmits the instruction from the host 10to the first connection destination storage control apparatus 200, andcauses the instruction from the host 10 to be transferred to the secondconnection destination storage control apparatus 300.

The controller 201 of the first connection destination storage controlapparatus 200, upon receiving the instruction from the controller 101(S124), transfers the instruction to the controller 301 of the secondconnection destination storage control apparatus 300 (S125).

Upon receiving the instruction from the controller 201 (S126), thecontroller 301 of the second connection destination storage controlapparatus 300 executes the specified function (S127), and notifies thecontroller 201 of the completion of processing (S128).

The controller 201, upon receiving notification of the completion ofprocessing from the controller 301 (S129), notifies the controller 101of the completion of processing (S130). The controller 101, uponreceiving notification of the completion of processing from thecontroller 201 (S131), notifies the host 10 of the completion ofprocessing (S132). The host 10, upon receiving notification from thecontroller 101 (S133), confirms that the processing specified in S121has been performed normally.

Thus in this embodiment, the first connection destination storagecontrol apparatus 200 is used as a command relay apparatus, and thesecond connection destination storage control apparatus 300 is used asthe final processing apparatus for the command. By this means, in thisembodiment the plurality of storage control apparatuses 100, 200, 300can be cascade-connected using external connection functions, and afunction requested by the host 10 can be caused to be executed by anappropriate storage control apparatus.

This invention is not limited to the above-described embodiments.Various additions and modifications can be made, within the scope of theinvention, by a practitioner of the art.

1. A storage system, comprising a first storage control apparatus whichaccepts request from a higher-level apparatus and at least one secondstorage control apparatus connected to enable communication with thefirst storage control apparatus, wherein the first storage controlapparatus can provide a second storage area of the second storagecontrol apparatus to the higher-level apparatus as a first storage areaof the first storage control apparatus, and the system comprising: astate detection section, which detects the state of the first storagecontrol apparatus and of the second storage control apparatus; afunction management section for managing functions which can be executedby the first storage control apparatus and by the second storage controlapparatus; an executing apparatus judgment section, which, whenexecution of a prescribed function is requested by the higher-levelapparatus, uses the state detection section and the function managementsection to judge which storage control apparatus among the storagecontrol apparatuses should execute the prescribed function, based on thestate of the storage control apparatuses and the details of theprescribed function; and, an execution instruction section, whichinstructs the storage control apparatus determined by the executingapparatus judgment section to be the storage control apparatus toexecute the prescribed function.
 2. The storage system according toclaim 1, further comprising a function selection section to select inadvance executable functions among the functions possessed by each ofthe storage control apparatuses, wherein the function management sectionmanages, for each of the storage control apparatuses, functions selectedby the function selection section.
 3. The storage system according toclaim 1, further comprising an execution mode setting section forsetting the execution mode of functions which can be executed by thestorage control apparatuses.
 4. The storage system according to claim 1,wherein conditions are set in advance for execution of each functionwhich can be executed by the storage control apparatuses, and theexecuting apparatus judgment section judges which storage controlapparatus among the storage control apparatuses should execute theprescribed function, based on the state of the storage controlapparatuses and on the conditions associated in advance with theprescribed function.
 5. The storage system according to claim 4,wherein, as the condition, when a load on the first storage controlapparatus is equal to or greater than a first threshold set in advance,the prescribed function is set to be executed by the second storagecontrol apparatus.
 6. The storage system according to claim 4, wherein,as the condition, when a load on the second storage control apparatus isless than a second threshold set in advance, the prescribed function isset to be executed by the second storage control apparatus.
 7. Thestorage system according to claim 4, wherein, as the condition, when theload on the first storage control apparatus is equal to or greater thana first threshold set in advance, and moreover the load on the secondstorage control apparatus is less than a second threshold set inadvance, the prescribed function is set to be executed by the secondstorage control apparatus.
 8. The storage system according to claim 1,wherein functions which can be executed by the first storage controlapparatus and by the second storage control apparatus can be dividedinto common functions which can be executed by each of the storagecontrol apparatuses, and special functions which can be executed by onlyone among the storage control apparatuses, and settings can be set inadvance indicating, for the common functions, which storage controlapparatus among the storage control apparatuses should be caused toexecute the functions.
 9. The storage system according to claim 1,wherein functions which can be executed by the first storage controlapparatus and by the second storage control apparatus can be dividedinto common functions which can be executed by each of the storagecontrol apparatuses, and special functions which can be executed by onlyone among the storage control apparatuses, and the executing apparatusjudgment section: (1) for the common functions, when the first storagecontrol apparatus can execute the common function, causes the firststorage control apparatus to execute the common function, and when thefirst storage control apparatus cannot execute the common function,causes the second storage control apparatus to execute the commonfunction based on the state of the second storage control apparatus; and(2) for the special functions, causes the second storage controlapparatus to execute the special function based on the state of thesecond storage control apparatus.
 10. The storage system according toclaim 1, wherein the prescribed function is a function which isaccompanied by data conversion, the first storage control apparatus andthe second storage control apparatus are capable of executing theprescribed functions, and when the first storage control apparatusexecutes the prescribed function, execution of the prescribed functionby the first storage control apparatus is set to valid and execution ofthe prescribed function by the second storage control apparatus is setto invalid, whereas when the second storage control apparatus executesthe prescribed function, execution of the prescribed function by thefirst storage control apparatus is set to invalid and execution of theprescribed function by the second storage control apparatus is set tovalid.
 11. The storage system according to claim 10, wherein thefunction accompanied by data conversion comprises at least one ofcompression and encryption.
 12. The storage system according to claim 1,wherein the higher-level apparatus requests execution of the prescribedfunction to the first storage area, and when the second storage controlapparatus is determined to be the executing storage control apparatus bythe executing apparatus judgment section, the execution instructionsection issues an execution instruction to cause execution of theprescribed function to the second storage area.
 13. The storage systemaccording to claim 1, wherein the plurality of second storage controlapparatuses are each connected to the first storage control apparatus soas to enable communication, and each of the second storage controlapparatuses are interconnected so as to enable communication, theexecution instruction section issues an execution instruction to thesecond storage control apparatus determined to be the executing storagecontrol apparatus by the executing apparatus judgment section from amongthe plurality of second storage control apparatuses, to cause executionof the prescribed function; and, the execution instruction thus issuedis transmitted via second storage control apparatus not selected as theexecuting storage control apparatus by the executing apparatus judgmentsection, to the second storage control apparatus determined to be theexecuting storage control apparatus.
 14. The storage system according toclaim 1, wherein the prescribed function comprises at least one of datacopying within the second storage control apparatus, and a powermanagement function for storage devices of the second storage area. 15.A storage control apparatus connected so as to enable communication witha higher-level apparatus which requests execution of prescribedfunctions and with a second storage control apparatus, a second storagearea of the second storage control apparatus being able to be providedin virtual form to the higher-level apparatus as a first storage area ofthe storage control apparatus itself, the storage control apparatuscomprising: a state detection section, which detects the state of thestorage control apparatus itself and of the second storage controlapparatus; a function management section for managing functions whichcan be executed by the storage control apparatus itself and by thesecond storage control apparatus; an executing apparatus judgmentsection, which, when execution of the prescribed function is requestedby the higher-level apparatus, uses the state detection section and thefunction management section to judge whether the storage controlapparatus itself or the second storage control apparatus should executethe prescribed function, based on the state of the storage controlapparatus itself and the second storage control apparatus and on thedetails of the prescribed function; and, an execution instructionsection, which instructs the storage control apparatus determined by theexecuting apparatus judgment section to be the storage control apparatusto execute the prescribed function.
 16. A storage system, comprising afirst storage control apparatus which accepts requests from ahigher-level apparatus and a plurality of second storage controlapparatuses connected with the first storage control apparatus so as toenable communication, wherein the first storage control apparatuscomprises at least a first controller; each of the second storagecontrol apparatuses comprises a second controller to execute specifiedfunctions and a plurality of storage devices; the first controllerprovides logical volumes, created on intermediate storage devices, tothe higher-level apparatus, by associating one or a plurality ofintermediate storage devices, provided in virtual form within the firststorage control apparatus, with physical storage areas provided by thestorage devices of the second storage control apparatuses; and the firstcontroller comprises: a volume management table, which manages therelations between the logical volumes, and the intermediate storagedevices and the storage devices of each of the second storage controlapparatuses; a function management table, in which are registeredfunctions which can be executed by the first storage control apparatusand by each of the second storage control apparatuses; a functionexecuting apparatus management table, which sets in advance, for thegroup of functions which can be executed by any of the second storagecontrol apparatuses among the functions registered in the functionmanagement table, which of the second storage control apparatuses is tobe caused to execute each function; a state detection section, whichdetects the load state of the first storage control apparatus and of thesecond storage control apparatuses; an executing apparatus judgmentsection, which, when execution of a prescribed function has beenrequested by the higher-level apparatus, uses the state detectionsection, the function management table, and the function executingapparatus management table to judge which storage control apparatusamong the first storage control apparatus and the second storage controlapparatuses should execute the prescribed function, based on the stateof the first storage control apparatus and the second storage controlapparatuses and on the details of the prescribed function; and anexecution instruction section, which instructs the first controller orthe second controller of the storage control apparatus determined to bethe executing storage control apparatus by the executing apparatusjudgment section to execute the prescribed function.